Machine tools such as cut-off tools which are mounted on a lathe turret or a similar tool holder are subjected to very strong distorting and deflecting forces, arising from the interaction of the cutting element and the metallic workpiece. The high speed demanded by lathe tool operations produces rapid vibrations which must be counteracted or absorbed, to prevent unnecessary play and lost motion. Tool geometry, tool speed, feed rate and similar factors can be designed to improve the performance of the tools and to overcome the dynamic instability resulting from the vibrations, although the complicated relationship between the cutting variables impose restrictions on the feasability of technical improvements. Prior art includes U.S. Pat. Nos. 256,668, 517,167, 902,169, 2,243,239, 3,140,627, 3,688,366 and 3,731,356.
The present invention is directed to resolve the various problems inherent in conventional designs by providing a cut-off tool holder for a metal cut-off tool which has sufficient rigidity for improved performance and hence, production, and which also permits rapid and easy adjustment or replacement of the cut-off tool for grinding and sharpening.
More specifically, the cut-off tool holder, according to the present invention, includes a substantially rectangular support block with a seating member which is inserted into a slot of the lathe turret and secured to the support block by a hexagonal nut. At its end opposite its attachment to the lathe turret, the support block has a horizontal shoulder formed in its side wall on which an elongated cutting element of rectangular cross-section is supported over part of its length. The shoulder is a predetermined distance, for most lathes, 0.5 or 0.375 inch, above the bottom surface of the tool holder. The cutting element which has a cutting blade at one of its ends is clamped against the support block by an overhead lid which includes a recess in which the upper portion of the cutting element is received. A plurality of helical compression springs which are seated in depressions provided therefor in the support block, abut at their opposite ends against the underside of the lid. A groove of semi-circular cross-section is hollowed out of the top surface of the support block, parallel to the orientation of the cutting element, and opens toward a mating identical groove formed on the underside of the clamping lid. Together, the grooves form a tubular enclosure for a cylindrical hingepin whose center section is joined at both ends to coaxial end sections of reduced diameter. The diameter of the tubular enclosure is slightly larger than the diameter of the center section of the hingepin which fits snugly thereagainst. The hingepin is formed with retaining ends normal to the axis thereof, and is disposed at the exterior of the support block and of the lid thereabove, parallel with and adjacent to the respective sidewalls, to hold the hingepin centered in the tubular enclosure. The opposite end of the tool holder is formed with a channel for securely receiving a turning or cut-off tool, pivotable to the back of the stock.